- Tris(5-aryl-1,3,4-oxadiazolyl)benzotrithiophenes – Discotic Liquid Crystals with Enormous Mesophase Ranges
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C3-symmetrical, alkoxyphenyl substituted 2,5,8-(tris-1,3,4-oxadiazol-2-yl)benzo [1,2-b; 3,4-b′; 5,6-b′′]trithiophenes (OXD-BTT) are synthesized via threefold Huisgen-reaction. A broad variation of alkoxy substitution pattern and chain lengths is reported. The thermal behavior was investigated via differential scanning calorimetry (DSC), polarized optical microscopy (POM) and thermogravimetry (TGA). Optical properties were studied via UV-Vis and fluorescence spectroscopy. Structural information of the LC phases was gained from X-ray diffraction on oriented fibers. OXD-BTT provide enormous phase widths (ΔT≥289 K) with clearing points close to thermal decomposition. Most of the derivatives exhibit two different mesophases, the lower phase with a rectangular 3D-structure and a hexagonal 2D-lattice at higher temperature. The variation of the chain length allows a tuning of melting and clearing points. OXD-BTT emit blue light with fluorescence quantum yields up to 30 % in good solvents. The emission is very sensitive to aggregation, thus, in poor solvents the emission intensity decreases, and red shift of maxima occurs.
- Tober, Natalie,Winter, Johannes,Jochem, Matthias,Lehmann, Matthias,Detert, Heiner
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supporting information
p. 798 - 809
(2021/02/01)
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- Unusual multistep reaction of C70Cl10 with thiols producing C70[SR]5H
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We report a reaction of the chlorofullerene C70Cl10 with thiols producing C70[SR]5H with all organic addends attached around one central pentagon at the pole of the C70 cage. This reaction was shown to proceed via a complicated radical pathway, presumably involving addition, substitution, rearrangement, and/or elimination steps. The obtained C70[SR]5H products were shown to be very unstable and undergo quantitative decomposition to pristine C70, RSSR, and RSH at elevated temperatures (e.g., 50 °C). Quantum chemical calculations and NMR spectroscopy data showed that cleavage of organic addends from the fullerene cage could be induced by solvation effects in solution.
- Khakina, Ekaterina A.,Peregudov, Alexander S.,Yurkova, Anastasiya A.,Piven, Natalya P.,Shestakov, Alexander F.,Troshin, Pavel A.
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p. 1215 - 1219
(2016/03/01)
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- Biofunctional silicon nanoparticles by means of thiol-ene click chemistry
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The preparation and characterization of butylene-terminated silicon nanoparticles (SiNPs) and their functionalization using thiol-ene chemistry is described, as well as the coupling of DNA strands. Bromide-terminated SiNPs were prepared by means of the oxidation of magnesium silicide and functionalized with butylene chains through treatment with the corresponding Grignard reagent. The successful coupling was confirmed by NMR and FTIR spectroscopy. TEM measurements revealed a silicon-core diameter of (2.4±0.5)nm. The fluorescence emission maximum is at λmax=525nm when excited at λexc=430nm. The conjugation of these alkene-terminated SiNPs by means of thiol-ene chemistry is described for a variety of functional thiols. Efficient coupling was evidenced by NMR and FTIR spectroscopy. Moreover, the characteristic fluorescence properties of the SiNPs remained unaltered, thus demonstrating the value of this approach towards functional oxide-free SiNPs. Activation of the attached carboxylic acid moieties allowed for conjugation of NH2-terminated oligo-ssDNA (ss=single strand) to the SiNPs. Successful coupling was confirmed by a characteristic new UV absorption band at 260nm, and by the still-present distinctive fluorescence of the SiNPs at 525nm. Gel electrophoresis confirmed coupling of 2 to 3 DNA strands onto the SiNPs, whereas no uncoupled DNA was observed.
- Ruizendaal, Loes,Pujari, Sidharam P.,Gevaerts, Veronique,Paulusse, Jos M. J.,Zuilhof, Han
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supporting information; experimental part
p. 2776 - 2786
(2012/06/01)
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- Regioselective synthesis of poly-substituted thiophenes from Baylis-Hillman adducts
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The reaction of Baylis-Hillman acetates and ethyl mercaptoacetat e in the presence of DBU in DMF produced 2,3,4-trisubstituted tetrahydrothiophenes at room temperature as a diastereomeric mixture via the sequential SN2' and Michael addition. Aromatization of tetrahydrothiophenes by DDQ oxidation produced 2,3,4-trisubstituted thiophenes in good yields.
- Lee, Hyun Seung,Kim, Se Hee,Kim, Jae Nyoung
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scheme or table
p. 6480 - 6483
(2011/02/21)
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- Synthesis and effect of two new penetration enhancers on the transdermal delivery of 5-fluorouracil through excised rat skin
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The tetrahydrogeraniol (THG) derivative, ethyl-(3,7-dimethyl octyl thio) acetate (EDOTA) was prepared by reacting tetrahydrogeranyl bromide (obtained by reaction of 40% hydrobromic acid and concentrated sulfuric acid) with ethyl 2-mercaptoacetate, while 3,7-dimethyl octyl propionate (DOP) was synthesized by a common esterification reaction by reacting THG with propionic acid in the presence of cyclohexane and concentrated sulfuric acid. The penetration-enhancing effect of the new enhancers were compared with THG and Azone in vitro using excised rat skin in modified Franz-type diffusion cells. 5-Fluorouracil (5-FU), a hydrophilic drug with poor skin permeability was used as a model permeant. Skin samples were pretreated with pure liquid enhancers for 12 h. 5-FU flux through the control and enhancer-treated skin increased linearly with its concentration in the receptor compartment. EDOTA and DOP interacted with the skin rapidly (2 h), and the duration of action is at least 24 h. Significant differences were found in the flux values of 5- FU; EDOTA and DOP enhanced the permeability of the drug about 6-fold and 11- fold respectively. Increased partition coefficient and diffusion coefficient values were obtained by these enhancers. The results suggested that the amount of EDOTA and DOP in the skin, especially in the stratum corneum, may be related to their penetration-enhancing effect.
- Hanif, Raja Muhammad,Qineng, Ping,Fenzhu, Muo
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p. 1428 - 1431
(2007/10/03)
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- Preparation of New Nitrogen-Bridged Heterocycles. 42.1 Synthesis and the Reaction of Pyridinium N-Ylides Using Bifunctional Ethyl Thiocyanatoacetates
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Various pyridinium (monosubstituted methylide)s were smoothly attacked to the cyano group in ethyl thiocyanatoacetate or ethyl 2-thiocyanatopropionate to afford the corresponding pyridinium (substituted cyanomethylide)s in low-to-moderate yields, while pyridinium (unsubstituted amidate)s reacted with the ester carbonyl group in the same reagents to give pyridinium (thiocyanatoaceto)- or (2-thiocyanatopropiono)amidates in considerable yields. The 1,3-dipolar cycloadditions of some pyridinium (unsymmetrically substituted cyanomethylide)s with dimethyl acetylenedicarboxylate (DMAD) in various solvents afforded only dimethyl 3-cyanoindolizine-1,2-dicarboxylate, except a few examples. On the other hand, the treatment of pyridinium (thiocyanatoaceto)- or (2-thiocyanatopropiono)amidates with a strong base, such as potassium t-butoxide, gave new bicyclic mesoionic compounds, N-[2-(1,3,4-thiadiazolo(3,2-a]pyridinio)]acetamidate derivatives, in moderate yields. The intermediacy of N-[1-(2-thiocyanatopyridinio)]acetamidates in the formation reactions of the latter compounds was also proven by independent syntheses.
- Kakehi, Akikazu,Ito, Suketaka,Hashimoto, Yasunobu
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p. 1769 - 1776
(2007/10/03)
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- Direct synthesis of thiols from halides and epoxides using hydrosulfide exchange resin in methanol
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Various thiols are prepared directly from the corresponding alkyl halides and epoxides using hydrosulfide exchange resin in methanol in the presence of equimolar amounts of triethylammonium chloride at room temperature. The reaction not only proceeds with unique chemoselectivity, but also gives better yields of thiols than most commonly used indirect methods and has an additional advantage of a simple workup.
- Choi,Yoon
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p. 373 - 375
(2007/10/02)
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- Substitution and Ring Closure Reactions of Phthalazine Derivatives
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1-(Phenylthio)- and 1-(hydroxycarbonylmethylthio)-4-methylphthalazines were prepared from 1-chloro-4-methylphthalazines (1).A series of 2-benzyl- and benzenesulfonyl derivatives was prepared from the corresponding halides and 4-methyl-1(2H)-phthalazinone (4). 4-Methyl-1(2H)-phthalazinthione (6) was substituted at SH group to give 1-(benzylthio)- and 1-(ethoxycarbonylmethylthio)-4-methylphthalazines, 7 and 8 respectively.Treatment of hydrazine hydrate with 8 produced 1-hydrazino-4-methylphthalazine (10).However, when the latter compound was treated with 1 it gave 1,2-bis-(4-methylphthalazinyl)hydrazine.Treatment of 10 with aromatic aldehydes in glacial acetic acid gave the corresponding 3-phenyl-s-triazolo-6-methylphthalazines 13. 1-Hydrazino-4-methylphthalazine (10) underwent cyclization reactions with acetic anhydride, ethyl chloroformate, carbon disulphide, ethyl formate, ethyl oxalate and with nitrous acid to give the corresponding triazolo-, triazino- and tetrazolophthalazine compounds.
- Badr, M. Z. A.,El-Sherief, H. A.,El-Naggar, G. M.,Mahgoub, S. A.
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p. 471 - 475
(2007/10/02)
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- Rate and Equilibrium Constants for the Reaction of Thiolate Ions with Dibenzo-1,2-dithiin and Naphtho-1,2-dithiole 1,1-Dioxides
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In aqueous dioxane the cyclic thiosulfonate dibenzo-1,2-dithiin 1,1-dioxide (1) reacts rapidly with thiolate ions and undergoes opening of the thiosulfonate ring (eq 2), forming disulfide 3a.Acidification of solutions of 3a with carboxylic acid buffers of appropiate pH leads to facile reversal of ring-opening reaction and the quantitative regeneration of 1.Since this reversal of ring opening is not acid-catalyzed, it must take place via a simple intramolecular displacement of RS- by the sulfinate (SO2-) group present in 3a and is therefore the microscopic reverse of the ring-opening reaction.Rate constants have been determined for both ring opening (kRS) and reversal of ring opening (k-RS) for a series of alkanethiolates of varying pKa.From these data one may also calculate the equilibrium constant, Keq(=kRS/k-RS), for reaction of each thiolate with 1.From comparison of the log Keq's with previously determined equilibrium constants for reaction of cyanide and sulfite ions with 1 one obtains quantitative information on the thermodynamics of reactions of the type ArSSR + CN- = ArSCN + RS- and ArSSR + SO32- = ArSSO3- + RS- that should be of considerable value for predicting the magnitude of equilibrium constants for cyanide-disulfide and sulfite-disulfide equilibria.Plots of log Keq, log KRS, and log k-RS vs. the pKa of RSH reveal that βeq=1.25, βRS=0.26, and β-RS=-0.99.These β values show that the transition state for eq 2 is quite unsymmetrical, with a structure Δ-...S-SO2δ-> where the RS-S bond is only ca. 20percent formed.The βRS and β-RS values are compared with the β values for several other previously studied displacements involving disulfides.The reaction of naphthol-1,2-dithiole 1,1-dioxide (2) with thiolates behaves in a fashion analogous to that of the reaction of RS- with 1.Comparison of Keq, kRS, and k-RS for an equilibrium involving 2 and a thiolate with those for the corresponding thiolate reacting with 1 allows one to assess how a change from a six- to a five-membered thiosulfonate ring influences Keq, kRS, and k-RS.The major effects are that k-RS is much larger and Keq is considerably smaller.
- Boduszek, Bogdan,Kice, John L.
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p. 2055 - 2060
(2007/10/02)
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- Reactions of Thiols with Phenylglyoxal to Give Thiomandelic S-Esters Formation of Hemithioacetals and Their Rearrangement
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Equilibrium constants Kh for the addition of 2-mercaptoethanol and glutathione to phenylglyoxal to form hemithioacetals were determined spectrophotometrically over the pH range 7-10.The observed Kh values decrease sigmoidally with pH as the thiol ionizes.Rearrangement of hemithioacetals formed from phenylglyoxal and various thiols was kinetically investigated.The rates increase with thiol concentration following a saturation curve to give Kh identical with the spectrophotometric value.The rearrangement is subject to general base catalysis.The solvent isotope effect on the rate of the rearrangement, kH2O/kd2O, is nearly 1.0; that on the equilibrium, KH2Oh/KD2Oh, is 0.38.The results strongly support the mechanism involving proton transfers through an enediol intermediate.
- Okuyama, Tadashi,Kimura, Kazumasa,Fueno, Takayuki
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p. 1493 - 1497
(2007/10/02)
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- Pesticidal compositions containing phosphoric esters and divalent sulphur compounds
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Pesticidal composition comprising: a pesticidal, phosphoric ester the molecule of which has at least one alkyl group of 1 to 3 carbon atoms, 0.05 to 10% of an agent stabilizing the said ester against decomposition by protonisation, together with adjuvants characterized in that the stabilizing agent comprises at least one sulphur compound containing per molecule at least one divalent sulphur atom of which one valence is bonded to an atom chosen from sulphur, carbon, nitrogen, hydrogen, and metals capable of giving a salt, the other valence being bonded to an atom chosen from hydrogen, the carbon atom already noted, a second carbon atom, the nitrogen atom already noted, a second nitrogen atom, the metal atom already noted in the case of a metal of valence greater than one, a second atom of metal and oxygen when the first valence is not attached to an atom of hydrogen, the proportion of sulphur calculated with reference to the weight of the sulphur compound being between 5 and 99%. Process for stabilizing a phosphoric ester of which the molecule possesses at least one alkyl group containing 1 to 3 carbon atoms characterized in that there is added to the phosphoric ester or to a mixture which contains it, 0.05 to 10% calculated on the weight of the phosphoric acid ester of an agent capable of stabilizing the said phosphoric ester against protonisation and comprising at least one sulphur compound such as that defined thereupon.
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- 3-Aryl-2-halothiopropionic acid s-esters
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Novel 3-aryl-2-halothiopropionic acid compounds of the formula STR1 wherein X is chlorine or bromine, R1 is hydrogen, a salt-forming cation, an aliphatic radical or a substituted aliphatic radical wherein the substituent is halogen, haloalkyl, hydroxy, alkoxy, alkoxy-carbonyl or aryl, R2 is hydrogen, halogen or alkyl R3 is hydrogen or alkyl n is an integer from 0 to 3; and R4 is halogen, alkyl, haloalkyl or nitro and wherein the radical R4, when n is 2 or 3, may be the same or different, Are outstandingly effective herbicides, exhibiting particularly selective action.
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